There’s a back street in Montparnasse, the entrance to a hospital morgue, where weeds grow in sidewalk cracks and beer cans rust on the pavement. The only discernible sign of life is a corner cafe, but even that feels more like the backdrop of a Cartier-Bresson photograph than a place to purchase actual coffee. On a clammy afternoon in August, the owner sits outside alone, smoking.

This narrow, nondescript passage — known as the Impasse Ronsin — was once an artery of aesthetic energy that, in no small fashion, defined French postwar art in all its insanity. First the site of the sculptor Constantin Brancusi’s studio, Ronsin was later where the likes of Max Ernst, Yves Klein, Niki de Saint Phalle and Jean Tinguely all lived or worked for much of the 1950s and early 1960s. For a moment in time, the alley was Paris itself, the lifeblood of an era.

What bears remembering is that the artists there were never just contemporaries; they were neighbors, a group shaped by many things but most of all by literal proximity — drinking, romancing and creating in a labyrinth of abandoned sheds hidden behind a frightfully dull streetscape. Collaboration on the Impasse never took the form of planned coordination; it was the precondition. It was a collective, a place where a generation of deft hands matured as artists and as people.

In the beginning, it was murder — not art — that christened the street. Impasse Ronsin was the address of Marguerite Steinheil, the consummate femme fatale and lover of many prominent men, including the French President at the time, Félix Faure. One by one, people close to Steinheil started dying. Faure’s final moment occurred during one of their trysts in 1899, allegedly midfellatio, and her husband and stepmother were strangled in their rooms in 1908. Steinheil was never convicted, but she fled to England anyway, leaving behind the house immortalized in tabloid scandal.

The artists started to arrive as early as the 1910s, attracted to the prospect of stand-alone ateliers whose squalor guaranteed bargain rents. As for Steinheil’s abandoned villa, according to the sculptor Claude Lalanne, who with her husband, François-Xavier Lalanne, lived on the alley in the ’50s, “We went there for the toilet.”

Ronsin eventually became something of a toilet itself, devoid of any sanitation, plumbing or heating save for what was left at Steinheil’s. By the time they were seized by the hospital in 1980, the Ronsin studios — which the French government had already declared unfit for habitation in the ’50s — had been vacant for almost 20 years and still had dirt floors. “This was not romantic,” recalls the American author Harry Mathews, 86, who arrived in the 1950s with his then-wife, Niki de Saint Phalle. “I don’t think anyone who has not seen the Impasse Ronsin as it was can imagine its squalor,” he says. For Claude, however, that was always immaterial, as the place was not a place: “It was,” she says, “une époque.”

Although Marguerite Steinheil was its patron saint, the real story of Ronsin begins with Brancusi, the Romanian émigré sculptor who arrived in 1916, in the midst of the First World War. Two generations older than the artists who came later, Brancusi was in many ways the alley’s self-appointed bon-papa, ruling benevolently until his death in 1957.

It was here — first in 8 Impasse Ronsin, then the more expansive 11 — that he created the bulk of his work, the rustic sculptures that celebrate the naked intensity of raw materials: marble, wood, metal. In 1927, he took on a 22-year-old Japanese-American apprentice who would memorize the lessons of the master even though the two could never communicate in any spoken language. “To give matter another role than the one nature intended it to have is to kill it” — this was how the young man internalized Brancusi’s central dictum. His name was Isamu Noguchi.

Claude Lalanne, who is now in her 90s, is one of the last surviving members of the original Ronsin set. During her time there, she and her husband designed many of the monumental bronze visions of flora and fauna that would later become their trademark, adorning the courtyards of public housing projects, the cover of a Serge Gainsbourg album and the library of Yves Saint Laurent and Pierre Bergé. (She also sculpted a bronze butterfly jewelry box, which we discusses in detail here.) But on the Impasse, “Les Lalanne,” as they were later known, were just a young couple, living next door to an old Romanian who came around with vodka most nights.

Claude remembers Brancusi as mercurial, the kind of character whose genius was often expressed in arbitrary edicts that could never be explained. He loved Asti spumante; he hated Max Ernst. “When he goes past, he steals my vital spirit,” she remembers Brancusi complaining about Ernst. When Claude complained to Brancusi that he threw too many cigarette butts on her floor, he gifted her with a metal bowl he made, which became a kind of Ronsin talisman. The Lalannes used it as an ashtray, Jean Tinguely as a part of one of his sculptures and, finally, the American sculptor James Metcalf as a casserole dish.

That dish was only the beginning of what the artists would share: a single toilet but many beds, cheap food but priceless ideas. It was there, in 1958, that Yves Klein and Jean Tinguely made “Excavatrice de l’Espace,” their joint argument that real art exists beyond any material object, in the ether around it. The sculpture itself is not much to look at, a wooden Tinguely machine mounted with awkward Klein monochrome panels. But when it moved, it created a zone of “pure color” that belonged only to a fleeting moment. The temporality was the art. As Claude recalls, Tinguely and Klein would work outside all day and, still covered in dust, retire for a simple entrecôte prepared on her primitive studio stove.

It was also on the Impasse Ronsin that, in 1961, Niki de Saint Phalle, a former cover girl, launched her career as an international artist with a literal bang. For her “shooting” canvases, she, along with friends such as Robert Rauschenberg, would fire guns into bags that concealed pockets of paint. This was somewhat of a Ronsin ritual, as Yves Klein had done much the same with the “Monotone-­Silence Symphony” the year before. He had conducted an orchestra as nude women danced covered in blue paint, plastering their bodies on canvas as they twirled. In both cases, what mattered was performance as much as product.

A sense of performance seemed to govern the artists’ personal lives as well. Ronsin was where de Saint Phalle left Harry Mathews to marry Tinguely, whose studio was directly across from Brancusi’s. Likewise, the American artist Larry Rivers eventually moved in with Clarice Price, his sons’ Welsh au pair. At one point or other, all of the women on the alley seem to have had — or at least contemplated — an affair with James Metcalf. There was even a Ronsin wedding in 1962, when Yves Klein married Rotraut Uecker, a young German artist. Christo painted their wedding portrait.

By the late 1960s, France was yet again in the midst of revolution, this time a social one. There was war in Vietnam, decolonization across the rest of the former French empire and the strident uprisings of May 1968. But these artists weren’t fueled exclusively by politics: Art historians have labeled them the “nouveaux réalistes,” leaders of a movement somewhere between the provocation of Dada and the materiality of Pop, but the truth is that there was little that united their respective projects.

And yet what they made on the Impasse Ronsin is how their moment is remembered. All museums are narratives, and the Centre Georges Pompidou, France’s national museum of modern and contemporary art, is a story that could never be told without this obscure Montparnasse alley. On the square outside Renzo Piano’s high-tech monolith, for instance, is a painstaking recreation of Brancusi’s original Ronsin studio, with the sculptures inside arranged exactly as he specified. On another side, there’s the Stravinsky Fountain by de Saint Phalle and Tinguely, a psychedelic dream manifested in rainbow plaster and constant streams of water. Inside, of course, there are Klein monochromes, beguilingly blue.

In a sense, the Impasse Ronsin was itself a kind of performance, the deliberate embrace of a primal, almost medieval existence in the heart of what Walter Benjamin called the “capital of the 19th century.” But in much the same way as the art that was made there, Ronsin itself was largely unrelated to its tangible reality, its gutters and grit. It, too, was a suggestion that, as Brancusi once observed, “What is real is not the external form but the essence of things.” That it no longer exists is entirely beside the point.

Correction:

An article on Sept. 25 about the Impasse Ronsin, an alleyway in Paris in which a number of famed artists of postwar France lived and worked in the 1950s and 1960s, described incorrectly the career of the artist Niki de Saint Phalle and the artwork she is shown creating by shooting at it with a .22 rifle. These artworks are considered paintings, not pictures. And at the time the photograph was taken, in June 1961, de Saint Phalle had been making this type of work since February of that year; it was not the first time she had created such a painting. The article also misstated the role the artist Christo played in the marriage of the artists Yves Klein and Rotraut Uecker. Christo painted the couple’s wedding portrait; he did not serve as the photographer in the ceremony.

From Oct. 27, 2016, to Jan. 18, 2017, “L’Impasse Ronsin,” an exhibit of works by artists who created there, will be shown at Paul Kasmin Gallery in New York City. A comprehensive monograph will accompany the exhibition.